There have been a number of recent news stories reporting that global warming pretty much stopped for the past decade, due to the cooling effect of increased sulfur output in China roughly cancelling, at least in the short term, the warming effect due to CO2. Assuming that the account is correct, I think it has an interesting implication, not for climate science but for the controversy around it.
I don't watch that controversy very carefully, but one part of it is the question of what is actually happening to global temperature, with some skeptics arguing that the upward trend is for one reason or another either fictional or exaggerated. My question is whether, prior to this particular explanation surfacing, the other side had conceded that for some unknown reason temperatures were not rising as predicted, or whether they waited to admit that until they had an explanation. If the latter, then perhaps the wrong side is getting labeled "denialist."
Can readers who are involved with the controversy, on one side or the other, point to evidence, claims and counterclaims about what was actually happening to global temperatures over the past decade?
A commenter provides a link that leads to a BBC interview with Phil Jones, who was a central figure in some of the recent climate controversy. He makes it reasonably clear that the recent data, while not inconsistent with the long-run warming trend, did not actually support it, which is evidence of the honesty of his side of the argument. The interview was, on internal evidence, between January 29 and February 13 of 2010, which I believe puts it well before the sulfur explanation had come out.
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A commenter provides a link that leads to a BBC interview with Phil Jones, who was a central figure in some of the recent climate controversy. He makes it reasonably clear that the recent data, while not inconsistent with the long-run warming trend, did not actually support it, which is evidence of the honesty of his side of the argument. The interview was, on internal evidence, between January 29 and February 13 of 2010, which I believe puts it well before the sulfur explanation had come out.
18 comments:
I recommend this piece over at Realclimate:
http://www.realclimate.org/index.php/archives/2009/07/warminginterrupted-much-ado-about-natural-variability/
"The contentious part of our paper is that the climate system appears to have had another 'episode' around the turn of the 21st century, coinciding with the much discussed 'halt' in global warming. Whether or not such a halt has really occurred is of course controversial (it appears quite marked in the HadCRUT3 data, less so in GISTEMP); only time will tell if it’s real."
Then read this that puts the above article in a different perspective:
http://www.worldclimatereport.com/index.php/2009/04/08/has-the-climate-recently-shifted/#more-371
"Unfortunately (for the modelers), is that the results from Swanson and Tsonis do not support a large real-world role of aerosols in determining the shape of the global temperature history. Instead of aerosols being responsible for the cooling from the 1940s through the mid-1970s and then the warming (accompanying a reduced aerosol load) from the late 1970s to the present (as in the models), Swanson and Tsonis explain these episodes by internal climate processes—no aerosols needed. In earlier work (Tsonis et al., 2007), the authors concluded that:
'The standard explanation for the post 1970s warming is that the radiative effect of greenhouse gases overcame shortwave reflection effects due to aerosols. However, [our result] suggests an alternative hypothesis, namely that the climate shifted after the 1970s event to a different state of a warmer climate, which may be superimposed on an anthropogenic warming trend’
Their new work further supports this conclusion as do plain and simple observations—after all, there is no way that declining influence of aerosols which was invoked to help explain the warming of the 1980s and 1990s can be used to explain the lack of warming thus far during the 21st century.
So if aerosols don’t play a large role in the 20th century temperature behavior, then the models get things right for the wrong reasons and, when fed the right reasons, they would get things wrong (i.e. produce too much warming—an indication that their climate sensitivity is too large).
The most important lesson of all that should be drawn from the work of Swanson and Tsonis is that the modeling community still has some important work to do, not only for projecting the future, but also for properly replicating the past. And until they can do the latter, they have no business even attempting the former.”
See this:
http://www.realclimate.org/index.php/archives/2009/07/warminginterrupted-much-ado-about-natural-variability/
"The contentious part of our paper is that the climate system appears to have had another 'episode' around the turn of the 21st century, coinciding with the much discussed 'halt' in global warming. Whether or not such a halt has really occurred is of course controversial (it appears quite marked in the HadCRUT3 data, less so in GISTEMP); only time will tell if it’s real."
And then this:
http://www.worldclimatereport.com/index.php/2009/04/08/has-the-climate-recently-shifted/#more-371
"… the biggest tuning knob for getting models to match reality is the one labeled ‘forcing from aerosols.’ This knob is especially useful because we really don’t know where exactly it should be set—thus different modeling groups can set it just about anywhere they would like to get their models to produce the right answer. The knob was installed in the first place because without it the models produce too much warming from greenhouse gas increases alone. So, add a knob that can be used to counteract some of that warming (taken together aerosols in the models produce a cooling), and you get the right answer without having to make any other major changes to the model!
...Unfortunately (for the modelers), is that the results from Swanson and Tsonis do not support a large real-world role of aerosols in determining the shape of the global temperature history. Instead of aerosols being responsible for the cooling from the 1940s through the mid-1970s and then the warming (accompanying a reduced aerosol load) from the late 1970s to the present (as in the models), Swanson and Tsonis explain these episodes by internal climate processes—no aerosols needed. In earlier work (Tsonis et al., 2007), the authors concluded that:
'The standard explanation for the post 1970s warming is that the radiative effect of greenhouse gases overcame shortwave reflection effects due to aerosols. However, [our result] suggests an alternative hypothesis, namely that the climate shifted after the 1970s event to a different state of a warmer climate, which may be superimposed on an anthropogenic warming trend’
Their new work further supports this conclusion as do plain and simple observations—after all, there is no way that declining influence of aerosols which was invoked to help explain the warming of the 1980s and 1990s can be used to explain the lack of warming thus far during the 21st century.
So if aerosols don’t play a large role in the 20th century temperature behavior, then the models get things right for the wrong reasons and, when fed the right reasons, they would get things wrong (i.e. produce too much warming—an indication that their climate sensitivity is too large).
The most important lesson of all that should be drawn from the work of Swanson and Tsonis is that the modeling community still has some important work to do, not only for projecting the future, but also for properly replicating the past. And until they can do the latter, they have no business even attempting the former.”
The decade of 200x has been warm but the rapid rise from ~1970-2000 has definitely decelerated. There's been a strong 60-year periodicity in the record (that the GCMs don't reproduce) which, if it continues, would mean a flat or slightly declining couple of decades coming up.
Lucia at http://rankexploits.com/musings/2011/noaa-may-cooler-than-april/
gives a good in-depth statistical overview of recent temps vs models.
Your description of the paper is wrong. They do not say that increased sulphur emissions cancelled out warming from CO2 but rather that they reduced the effect.
Temperature records are not secret and nobody disputes what happened to temperatures from 1998 to 2008. But that period is cherry picked -- starting with a strong El Nino and ending on a La Nina. The temperature record did not start in 1998 nor end in 2008. The point of the paper is to disprove claims that this cherry picked set of years shows that CO2 has no effect.
Quoting from Phil Jones interview:
BBC: Do you agree that from 1995 to the present there has been no statistically-significant global warming
Phil Jones: Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods. End quote.
My immediate source. Presumably you can also find the actual interview.
The author of the linked page helpfully explains:
The noisy signal means that over a short period, the uncertainty of the warming trend is almost as large as the actual trend. End quote.
And finally he says that the bigger picture is still warming:
When all the heat accumulating in the oceans, warming the land and atmosphere and melting ice is tallied up, we see that global warming is still happening. End quote.
I don't equate "roughly cancelling" with "cancelled out", but rather with the claim that the effect has at least been significantly reduced. Now, let's argue over "significantly".
Phil Jones actually changed his last June, see:
http://wattsupwiththat.com/2011/06/11/phil-jones-does-an-about-face-on-statistically-significant-warming/
He says that he can say that because data of 2010-2011 have changed the trend to "significant". That's strange, because 2010 was an El Nino year, and so the upward trend of that year should be taken with caution, as Tim, above, suggests.
The latest retcon reveals that these models do a wonderful job of retrodicting the data, but a piss poor job of predicting the data.
Today's temperatures are far below what the IPCC predicted in 2007 would be the lowest possible temperature.
They knew in 2007 that China's coal use was rapidly growing. The latest model is a retcon on their 2007 model
I think this comment by Judith Curry pretty well sums up my reaction to the paper:
Their argument is totally unconvincing to me. However, the link between flat/cooling global temperature and increased coal burning in China is certainly an interesting argument from a political perspective. The scientific motivation for this article seems to be that that scientists understand the evolution of global temperature forcing and that the answer is forced variability (not natural internal variability), and this explanation of the recent lack of warming supports a similar argument for the cooling between 1940 and 1970. The political consequence of this article seems to be that the simplest solution to global warming is for the Chinese to burn more coal, which they intend to do anyways.
And finally, with the civil heretic discussion fresh in my mind, I checked the personal web pages of each of the co-authors: Robert K. Kaufmann, Heikki Kauppi, Michael L. Mann (not Michael E. Mann, of hockeystick fame), and James H. Stock. These authors (individually and collectively) apparently know a heck of a lot less about atmospheric aerosols (i.e. pretty much nothing) than Freeman Dyson knows about climate change. The authors don’t seem to know much about attribution, either.
at http://judithcurry.com/2011/07/04/an-explanation-for-lack-of-warming-since-1998/
As to the question of whether this is a retcon, look at the GISS forcings page http://data.giss.nasa.gov/modelforce/ and observe the "reflective tropospheric aerosols" blue line. It flattens out after 1990. In other words, among the warmists, the ones who are real climate scientists didn't think much of that explanation.
I have encountered very few people who say that there is no global warming. The scientific question I see being asked is whether there will really be a positive feedback on top of the greenhouse effect of extra CO2 in the atmosphere. The greenhouse effect only raises the temperature 1 degree Celcius from a doubling of CO2. The IPCC claims we will see 3-4 times that increase, but a lot of cooler heads are skeptical.
We have not directly seen such accelerated warming so far. The explanation is that other emissions were counteracting the CO2. The claims about Chinese sulfates are the latest example of that pattern.
Not all climate scientists are convinced about the sulfate argument. For example, here's what Judith Curry has to say:
http://judithcurry.com/2011/07/04/an-explanation-for-lack-of-warming-since-1998/
Stepping back, I can't help but note a couple of other things about global warming, neither of which take a chemistry PhD:
1. The models have aren't predicting anything accurately. In addition to problems with bottom-line temperature, there have been problems with the patterns of warming at different layers of the atmosphere. The latter problem remains unexplained.
2. The earlier arguments for a vigorous response to CO2 emissions have mostly been abandoned. Michael Mann's hockey stick is abandoned, and the temperature record from surface stations is now widely regarded as too noisy to be useful. So we see a fixed conclusion with an ever-changing rationale.
--Daublin
As far as I know, there is no meaningful controversy in the scientific community. There are indeed lots of factors that contribute to changes in climate, and no one is denying that. And there's nothing deeply scientifically mysterious about short term cooling, either.
There's a close examination of how the short term data match up to IPCC projections here:
http://www.fool-me-once.com/2010/09/temperatures-are-below-projections.html
But I'm not sure that a close examination is really what we need here, though. If global temperature increases were the only issue that mattered for the future health of civilization, we could solve the problem pretty quickly by launching a significant fraction of the world's nuclear arsenal. Obviously this would be an unhealthy solution, but if degrees C were all we cared about, that would solve the problem quickly.
No one who is worried about environmental quality for human beings is going to argue that “burn more coal” is a good solution to global warming.
Descriptions of nineteenth century industrial cities make it clear that the particulate matter we'd be counting on to cool the earth is also not good for respiratory health.
Burning coal would still release CO2, which has the direct impact of acidifying the oceans, a process which is killing the coral reefs and doesn't look like it's going to be good for global fisheries either (http://www.scientificamerican.com/article.cfm?id=ocean-acidification-threatens-global-fisheries).
And we still haven't devised a method for extracting coal from the Earth that is healthy for both the workers (who are negatively affected by shaft mining) and for the people living downstream of the mines (who have to deal with a great deal of mineral contamination from surface mining).
Watch this documentary "Meat the Truth"to find out how most of the time we avoid talking about main causes of global warming. You may find this documentary in online film festival "Green Unplugged"
Global warming will always be in issue, as long man thinks he owns the whole world...
The entire AGW argument is a fraud. The IPCC, which was founded with a mandate to look at human effects on warming has ignored the peer reviewed evidence that makes it very clear that natural factors are the drivers of temperature trends, not CO2. This was fine when nature was cooperating and the state of the knowledge was poor but once temperatures began to cool and no statistically significant warming was evident the AGW proponents began to look for narratives to spin in order to hide the lack of empirical evidence to support their position.
The latest claim about Chinese emissions helping to 'cool' the planet is just the latest narrative. Keep in mind that early in the game we were told that the ice core evidence showed how CO2 concentration increases were driving temperature trends. But when increased resolution showed that the temperature trend change came first and that the CO2 followed 800 years later a narrative was spun to hide the inconvenient fact.
When the predicted equatorial mid-troposphere warm spot was shown to be absent from the empirical data the AGW proponents spun a story about how wind shear can be used to show that the nonexistent warming was really there.
Now we have the latest problem for the warmers. In a 2005 paper, which gets my vote for the worst timing award, Hansen and friends used the old ship readings and inaccurate floats to show how the radiative imbalance that is in the center of the AGW theory shows up as heat storage in the oceans. The authors used very simple calculations to predict what will happen in the future. Well, in 2003 the new ARGO system started to gather accurate temperature readings about ocean temperatures. That data shows that the predicted accumulation, which has to be there in order to show that the AGW theory has merit, is not there. And that is the reason why the AGW 'team' was so busy trying to find the "missing heat."
Sorry David but the emperor has no clothes. If my ten-year-old son can design an experiment to show that Jones' UHI estimates were ten to thirty times lower than what the empirical data suggests and use real time access to data to show that the IPCC should not have ignored the established UHI literature I am sure that smart people like your readers can do the same. This game has gone about as far as it can go. We have wasted far too much money subsidizing lousy alternative energy schemes and prevented the building of very necessary nuclear or fossil fuel based power generation facilities that are necessary for a healthy economy. It is time we began to act like grown ups and pointed out that the real world is very different than what the IPCC and the rent seekers in the green movement have said that it was.
The decade of 200x has been warm but the rapid rise from ~1970-2000 has definitely decelerated.
I do not know if the 2000s were all that warm. If you look at actual state highs you will find that in the US most records were set in the 1930s. And in 2007 Hansen was forced to admit that the 1930s were warmer and that 1934 was the warmest year.
The 'reported' highs that we see referenced come from 'adjusted' data that has seen computer algorithms add an artificial warming signal to the actual measurements and from 'imputed' temperatures that use stations as far as 1200 km to come up with Arctic temperatures that are plugged into the models. The simple fact is that all we really have to come up with the temperature profile is the CRU 'value-added' set, not actual measurements that came from real thermometers. This leaves out the use of the scientific method so all we have is a faith based process that makes up trends that cannot be replicated.
Final minus Raw: Magnitude of the total correction applied by NOAA
See the adjustment?
Jones has since reversed himself and claimed that warming since 1995 has now reached the level of "significance" not because there has been more warming but merely because there a year more figures. So much for honesty.
If, as often stated, you can judge a science on it predicative ability "the science of catastrophic global warming" doesn't quite match the "science of phrenology" and of astrology, both of which are right a statistically insignificant number of times.
I would be interested to see one numerical warming, or cooling prediction which turned out fully correct. Perhaps somebody van help.
It's a very young science, covering a dynamic nonlinear poorly understood natural system, practiced by few, and like all the others will be changing it's truths many times over the next century. Don't get caught up with each little dispute
David,
I think this puts the discussion of Sulphur and aerosols generally into context:
http://www.climate-skeptic.com/2011/07/return-of-the-plug.html
Basically, aerosols are a free variable which Global Climate Models (GCM) can use to make their predictions match up with reality. Since there are no reliable data for global aerosols, modelers are forced to estimate these numbers. And of course they always estimate them in ways which make their model match reality.
To my mind, this exposes how under-constrained the GCMs are. It's not clear they have any predictive power, or even how one would test their predictive power.
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